Discharge tube



June 5, 1928. 1,672,116

P. R. DIJKSTERHUIS DISCHARGE TI-JBE Filed Feb. 8, 1926 Patented June 5, 1928.

UNITED STA TESS 1,672,116 PATENT OFFICE.

POPKO REINDER .DIJ'KSTERHUIS. OF EINDHOVEN, NETHERLANDS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO RADIO CORPORATION OF AMERICA, OF NEW YORK, N. 1.,

A CORPORATION OF NEW YORK.

DISCHARGE TUBE.

Application filed February 8, 1926, Serial N'o.

Electric discharge tubes are known which comprise a hollow cathode, for example, a cylindrical oxide cathode heated by an electric heating element located inside the cathode, and iniwhich the leading-in wires for the said element, those for the cathode and those for the other electrodes pass through a single so-called pinch.

The invention has for its object to free the functioning of such a discharge tube from the disturbing electromagnetic as well as electro-static inductive influence originated by the said heating element. It is obvious that in particular the controlling electrode must be protected against these inductive influences.

According to the'invention, in order to realize this object, the leading-in wires for the heating element, for the cathode and for the other electrodes are led inwards through a single pinch, the leading-in wires for the heating element are located close to each other at one extreme side of the pinch, whereas theleading-in wires for the electrodes, in particular that for the controlling grid, if any, are located at the other end of the pinch so as to be as far remote as possible from the other leading-in wires.

Without any difliculty the heating element can be fed in this case with alternating current without the anode current being modulated in any detrimental manner by the frequency of this alternatingcurrent.

screening device near the opening of the cathode through which passes the heating element, between the other electrodes of the tube and that portion of the heating element which extends outside the cathode.

The cathode is preferably made of chrome iron, said material being easily deprived of occluded gases and being readily sealed to glass, which permits of sealing the open end of the cathode to the glass envelope of the tube so that the interior space of the cathode is accessible from the outside. .Consequently the heating element can easily be replaced by another without any necessity of taking the tube to pieces.

If in additionithe anode is also made of chrome iron and if the tube is constructed so as to have the greater portion of its outer wall constituted by the anode, a robust whole is obtained which neither has a fragile glass In most cases it is advisable to provide a 86,845, and in the Netherlands April 30, 1925.

and 18; the conductors 5 and 6 pass through one side of the pinch whereas a leading-in wire 10 for the rid 2 passes through the opposite side of t is pinch in order to keep the conductor 10 as far as possible apart from the conductors which are traversed by the alternating current for heating the filament,

In order to keep the grid 2 itself as much as possible out of the induction zone of the incandescent body 4, the cathode 1 is made materially longer than this incandescent bod and also materially longer than the gm 2. The cathode is preferably made of chrome iron and that portion of the outer surface which has to participate actively in the emission of electrons, is coated with a suitable active layer. The lead in wire 11 is I connected to the anode 3. Y

The conductive connection with the oathode is constituted by a metal clip 19 secured to a metal carrying rod 20 which passes through the pinch 15 and which supports at its top the spring 21 already mentioned. Thus a conductive connection is also obtained between the cathode l and the centre of the filament 4, which decreases still more the influence of the period of ie alternating current passing through the lament 4.

What I claim is:

1. In a discharge tube, anode, cathode and grid electrodes,a single pinch for the leads to the tube, a separate electrical heating element disposed adjacent to and heating the cathode, leads'to said heating element, said leads being disposed at one end of said single pinch, and a grid lead passing thru said pinch, said grid lead being positioned at the end of t e pinch opposite to the leads to the heating element.

2. A discharge tube having anode, cathode and grid electrodes, a single pinch for the leads to the tube, a separate electrical heating elementdisposed adjacent to and heating the cathode, leads to said heating element, said leads being disposed at one end of said single pinch, a lead passing thru said pinch and connected to the grid, said grid lead being positioned at the end'of the pinch opposite to the leads to the heating element, and a lead passing thru said pinch connected to the cathode.

3. A discharge tube having anode, cathode and grid electrodes, a single pinch for the leads to the tube, a separate electrical heating element disposed adjacent to' and heating the cathode, leads to said heating element, said leads being disposed at one end of said single pinch, a lead passing thru said pinch and connected to the grid, said grid lead being positioned at the end of the pinch opposite to the leads to the heating element, and a lead passing thru said pinch connected to the cathode, said anode and cathode leads being disposed between the heating element leads and the grid lead.

4. A discharge tube having anode, cathode and grid electrodes, said cathode being cylindrical, a single pinch for the leads" to the tube, a separate electrical heating element disposed Within the cathode, the length of the cathode being considerably longer than the heating element thereby serving as an electrical shield between the grid and the heating element leads to said heating element, said leads being disposed at one end of said single pinch, and a grid lead passing thru said pinch, said grid lead being positioned at the end of the pinchopposite to the leads to the heating element.

5. A discharge tube having anode, cathode and grid electrodes, said cathode being cylindrical, a single pinch for the leads to the tube, a separate V shaped electrical heating element disposed within the cathode, leads to said heating element, a support for said heating element positioned outside of the cylindrical cathode, said support having a portion extending within the end of the cathode opposite to the heating element leads and attached to the'point 01. the V of the heating element, said heating element leads being disposed at one end of said single pinch, and a grid lead passing thru said pinch, said grid lead being positioned at the end of the pinch opposite to the leads to the heating element 6. A discharge tube having anode, cathode and grid electrodes, said electrodes being disposed excentrically within the tube, a single pinch for the leads to the tube, a

separate heating element disposed adjacent.

to and heating the cathode, leads to said heating element, said leads being disposed at one end of the single pinch, and a rid lead passing thru said pinch, said grid lead being disposed at the end of the pinch op-, posite to the heating element leads, said grid lead extending within the tube eccentrically opposite from the electrodes and being connected to the end of the grid which is farthest from the heating element leads.

In testimony whereof I aflix my signature, at the city of Eindhoven, this l6th day of January, A. D. 1926.

POPKO REINDER DIJKSTERHUIS. 

